Background: To delay the onset of dementia, it is important for healthy adults to take preventive actions before the cognitive function clearly declines. Protein malnutrition is a potential risk factor for senile dementia, although the precise link between protein/amino acid nutrition and cognitive function is unknown. The purpose of this study was to examine the effect of the ingestion of seven selected essential amino acids as a granular powder, namely, leucine, phenylalanine, and lysine supplemented with isoleucine, histidine, valine, and tryptophan on cognitive and psychosocial functions in healthy adults.Methods: A double-blind, randomized, placebo-controlled trial was conducted. A total of 105 participants aged 55 years or older were randomly assigned to one of three groups: daily ingestion of 3 g (3gIG) or 6 g (6gIG) of the selected amino acids or daily ingestion of a placebo (PCG). Each group ingested the test powder for 12 weeks. As the main outcome, cognitive function was assessed before and after ingestion by a cognitive test battery. Psychosocial functions were also examined.Results: The numbers of participants excluding dropouts were 35 in PCG and 3gIG and 33 in 6gIG. Analysis of covariance revealed that the 6gIG showed significantly improved cognitive function (Trail Making Test B), social interaction and psychological health scores after ingestion compared to the PCG (multiplicity adjusted p < 0.05).Conclusions: Current findings suggested that ingestion of the seven essential amino acids led to improved attention and cognitive flexibility and psychosocial functioning, which is expected to prevent cognitive decline.Clinical Trial Registration: University Hospital Medical Information Network Clinical Trial Registry (URL: https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000037779, Identifier: UMIN000033174).

Background: To delay cognitive decline, it is important to engage actively in preventive activities from middle age (50–64 years of age). We have developed a cognitive intervention program using picture book reading, and demonstrated that it is effective for improving memory in older adults. However, the effect of the intervention on memory and other cognitive functions in middle-aged people has not been examined. The current study investigated the effects of the picture book reading program on cognitive function in middle-aged people.Methods: This single-blind (examiners were blinded) randomized controlled trial was conducted in Tokyo, Japan. A total of 65 participants were randomly assigned to the intervention group (IG) (n = 32), in which members attended 12 picture book reading classes held once a week, or the active control group (CG) (n = 33), in which members received lectures on health maintenance. Cognitive tests were conducted before and after the intervention. The primary outcome was memory, and the secondary outcomes were verbal function and executive function.Results: The results showed that there was no significant difference between the IG and the CG in change scores (post minus pre) for memory. On the other hand, there was a significant difference in change scores of the category fluency, which is a measure of verbal function, suggesting improvements in IG compared to CG. There were also no significant differences in executive function.Conclusions: The results indicated that our previous finding of an improvement in memory function in older adults was not found in middle-aged people. However, the findings suggest that the picture book reading program may affect lexical access ability in verbal function among middle-aged people. Because maintaining verbal function is important for daily communication, these findings suggest that this program may be a useful countermeasure for cognitive decline in middle-aged people.Clinical Trial Registration: University Hospital Medical Information Network Clinical Trial Registry, https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000048012, Identifier: UMIN 000042071

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